1. Field of the Invention
The present invention relates to a communication apparatus such as a facsimile apparatus capable of selective polling. It also relates to a communication apparatus such as a facsimile apparatus capable of performing communication using a sub-address signal.
2. Related Background Art
In conventional selective polling systems, a polling send station side declares presence of a function of selective polling to a polling receive station side, the polling receive station side transmits a DTC signal and an SEP signal, and the polling send station side performs polling transmission of information designated by the SEP signal.
However, such conventional systems cannot perform plural selective pollings.
In the case where plural selective pollings are required during one communication, an operator on the polling receive side cannot designate plural selective pollings unless confirming that the partner polling send station has a function for performing plural selective pollings during one communication. Such a selective polling system must be difficult to handle.
Further, in conventional facsimile apparatuses capable of performing communication using a sub-address signal, since it is not defined how to use the sub-address signal, facsimile transmission cannot be performed unless a user phones a partner user to determine how to use the sub-address signal before the facsimile transmission.
Thus, the user who intends confidential communication using the sub-address signal is required to phone an operator at a destination and obtain information associated with the sub-address signal for confidential transmission before setting the sub-address signal.
Although the sub-address signal can also be used for routing, the user is required in this case to phone a person at the destination as to what kind of apparatus is used at a terminal connected as a routed destination and how to designate the terminal, and thereafter set the sub-address signal.
As described above, the use of a sub-address signal always involves a phone call to the partner user, and it takes time very much.
At the partner side, it also takes a long time because an operator must receive an inquiry by phone each time sub-address communication is performed. This causes a great reduction in working efficiency.
According to the ITU-T recommendations T.30, sub-address communication is carried out by notifying to the partner station information associated with presence or absence of sub-address signal receiving capability by FIF (bit 49) of a DIS signal, and information associated with transmission of the sub-address signal by FIF (bit 49) of a DCS signal.
In this case, however, since only the information associated with the presence or absence of the sub-address signal receiving capability and information associated with the transmission of the sub-address signal are displayed, it is uncertain whether or not a sub-address signal different from the previous one can be sent from a transmitting apparatus when a communication mode is changed. In some conventional apparatuses, transmission of such a different sub-address signal may cause a communication error when the mode is changed, resulting in execution improper of communication.